Signal for telephone-switchboards.



No. 638,425. Patented Dee. 5,1899.

1:. E.- SGRIBNER. sna'mu. FOR TELEPHONE swncHBoAnns.

(Application filed Apr. 28, 1897.)

(No Model.)

hill

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERNELECTRIC COMPANY, OF SAME PLACE.

SIGNAL FOR TELEPHONE-SWITCHBOARDS.

SPECIFIGATION formingpart of Letters Patent No. 638,425, dated December5, 1899. Application filed April 23, 1897. Serial No. 633,447. (Nomodel.)

To aZZ whom it may concern.-

Be itknown that 1, CHARLES E. SCRIBNER, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certain new and usefulImprovementinSignalsfor'Ielephone-Switchboards, (Case No. l49,) of whichthe following is a full, clear, concise, and exact description,reference being had to the accompanying to drawing, forming a part ofthis specification.

This invention concerns signals associated with telephonelines intelephoneswitchboards designed to be controlled automatically in the useof the substation-telephones and serving to continuously inform theattendant at the switchboard of the condition of the substationappliances. It is a system of secondary electromagnetic signals and anelectromagnetic controlling device therefor '20 associated with the lineand responsive to changes in the electrical condition of the linedetermined in the use of the substation-telephone, this device servingto control both the line-signal and the supervisory signal at differenttimes, the purpose of the invention be ing to avoid as far as possibleclosed bridges of the line-circuit or magnets interposed in thetelephonic circuit. The signals comprise a line-signal permanentlyassociated with the 0 line and representing it in the switchboard and asupervisory signal adapted for temporary association with the lineduring connection with it.

The invention involves a mode of effecting the concealment of theline-signal when connection is made with the line in response to a call,a new arrangement of circuit connections whereby the display of theline-signal of a called line during the use of the latter is prevented,and means whereby the supervisory signals associated with the usualconnecting-plugs in the switchboard are brought temporarily under thecontrol of the electromagnetic signal-controlliug appliances of the 5united lines.

In constructing a commercial form of this invention I provide a relaywhich constitutes the signal-controlling appliance connected in apermanently-closed bridge of the line-cir- 5'0 cuit, including also asource of current, to-

gether with a switch at the substation automaticall y operated in theuse of the telephone to change the circuits at the substation andthereby to affect the relay, a local-battery circuit in the switchboardfor the relay and an electromagnetic visible line-signal having awinding in the local circuit and adapted to display its indicator whenexcited, a difierential and equal winding on the magnet of theline-signal, a circuit including this winding and means for closing thecircuit in the act of making connection with the line to render theline-signal inert, an extension of the local circuit controlled by therelay temporarily completed in registering contact pieces of theterminal spring-jack of the line and of the plug therein duringconnection with the line, and a supervisory signal in thistemporarily-extended circuit adapted to display its indicator whendeprived of current.

The invention involves also certain specific arrangements of circuitsfor securing a testsignal when the system is applied to multipleswitchboards, which will be fully set forth in the specification andclaims.

The invention is illustrated in the diagram hereto attached, whichrepresents two substations connected by telephone-lines withspring-jacks and signal-controlling relays in a telephone-switchboard,together with a pair of plugs for uniting the lines and signalsassociated with the plugs after the plan of this invention.

The usual call-bell, transmitting-telephone, receiving-telephone, andtelephone-switch are 8 5 provided at the substation, the bell being in aclosed bridge of the line, together with a condenser, and the telephonesbeing in the bridge of the line, which is normally open at the contactsof the switch. This arrangeo ment of circuits permits the closure of theline only while the telephone is in use. The line conductors 1 and 2extend from these appliances to the switchboard, where they traverse thewindings of a relay (1, whose 5 magnet should be characterized bysuitablyhigh impedance. After traversing the windings of this relay theline conductor 1 is led to earth, while conductor 2 is connected withthe free pole of a grounded batterybor other source of current. Theusual spring-jacks c and '0 form normally open terminals of the line inthe switchboard, the spring-jacks being located, if desired, upondifferent sections of a multiple board.

The relay a controls a local circuit 3 4, which includes a winding dofthe secondary line-signal d. The wire 3 leads from one pole of agrounded battery 6 to the movable contact-piece of the relay, while thewire iis an earth branch from the fixed contact-point of the relay. Fromthe latter wire 4 a conductor 5 is led to the ring or thimble contacts fof spring-jacks c and c. The signal d is of well-known type, consistingof a magnet with an extended curved pole-piece acting upon a pivotediron shutter, the action of the magnet when excited being to draw theshutter or indicator into a vertical position, in which it is displayed.

The usual connecting-plugs g and g are furnished for the use of theoperator in the switchboard. Each plug comprises three contact-sections72., h, and 72 which are designed to register with the thimble f andwith the two line-springs f and f of a spring-jack into which the plugmay be inserted. The contact-pieces h and 77. of the two plugs areunited by conductors 6 and 7, which consti tute the plug-circuit.Condensers t' and 11 are interposed in the conductors 6 and '7 to breakthe continuity of these conductors as to continuous currents, whilepermitting the flow of telephonic currents through the plugcircuitforthe purpose of maintaining independence of operation for thesignal-controlling relays a of two united lines. The usual calling-key7a is included in the plug-circuit, and a listening-key Z is furnishedto enable the operator to connect her-telephone m in a bridge of theplug-circuit.

The contact-pieces h of plugs g and g form the terminals of wires 8 and9, respectively, which lead to the free pole of a grounded battery n.The conductor 8 traverses the magnet-winding of a visible signal 0,which is associated in the switchboard with the plug g. Conductor 9includes the winding of a similar signal 0, which refers to plug g inthe switchboard. These signals are substantially like the line-signalscl, but differ in that their pole-pieces are arranged below the pivotedshutters in such a way that the shutters normally displayed are drawninto horizontal positions, where they are concealed, through the actionof the pole-pieces when the magnets are excited.

Inasmuch as the successful operation of this system depends to someextent on the proper adjustment of the resistances of the differentparts, the followingstatement of electrical dimensions may be taken asspecifying a typical arrangement. Each of the windings of the relay amay be of three hundred ohms. The battery Z) may have an electromotiveforce of twenty volts. The battery 6 may have an electromotive force ofsix volts and the batteryn two volts. The resistance of each of thewindings d and d of the signal d may be one hundred ohms and that ofeach of the signals 0 and 0 maybe forty ohms. A general statement of theessential relations between the resistances and electromotive forces inthe local circuits may be more clearly made in connection with thedescription of the cooperative functions of those parts.

The removal of the receiving-telephone from its switch at a substationpermits current to flow from battery I) in the line-circuit, whichexcites the magnet of relay aandcauses the latter to close the localcircuit which it controls. This action of the relay permits current toflow in the circuit 34, which, traversing the winding d of signal 01,excites this secondary signal and brings the shutter of the signal intoits vertical position, in which it is displayed to the operator. Thepresentation of this indicator signifies to the attendant that the userof the line with which the signal is associated is awaiting attention.She accordingly inserts plug g into the spring-jack c of the line andconnects her telephone with the plug-circuit 6 '7 by means oflistening-key Z, whereby she is brought into telephonic communicationwith the calling party. The insertion of the plug into the spring-jackcauses a rearrangement of the circuits, as follows: A path is completedfrom battery 0 through wire 3, thence through the contact-pieces of therelay to wired, including the winding d of the signal 01, and thencethrough the contact-pieces f of the spring-jack and h of the plug,conductor 8, including signal 0, and battery n to earth.

The current through the winding 61 should be of such strength as toneutralize the magnetizing effect of winding 61, rendering the magnetinert and permitting the indicator of the signal to return to its normalconcealed position. The current through the magnet of signal 0 shouldexcite this magnet and cause the withdrawal of its indicator from View.

Having learned from theperson calling the order for the connectionrequired, the operator may test the line called for-as, for instance,that to station A-in the usual way that is, by applying the tip of plugg to the thimble fof a spring-jack of the line. It will be observed thatin the ordinary condition of the apparatus no battery is connected withthe rings fof the spring-jacks of the line, and hence at such a time notest-signal would be produced in the operators telephone by the contactof the plug with the ring. When, however, the linerelay a of the linehas become excited and closed its local circuit, the battery 6 isconnected with the testrings, or when a connection has been made bymeans of a plug with the line the battery n is connected with the rings,in either of serts plug g into the spring-jack c and transmits asignaling-current by means of key to ring the bell at station A. Theuniting of wires 5 and 9 changes the electrical condition of thetest-rings in readiness for a subsequent test, while it also completes acircuit through winding d differential to winding cl, so that the magnetof signal (1 of the called line remains inert. The currentt-hrough signal 0 from battery it should be insufficient to excite that signal andeffect the concealment of its indicator, so that the indicator willremain in View. Its presence indicates to the attendant that thetelephone at the called station still remains on its switch. When thetelephone at that station is removed for use, the relay a becomesexcited, as before traced with reference to the callingline, andconnects the battery 6 with the conductors 4 and 5. Sufficient currentis thus produced through the magnet of signal 0 to conceal the indicatorof that signal, signalizing to the operator the response of the calledparty. Inasmuch as the current divides between windings d and cl of theline-signal d, however, the latter signal remains inert.

When the receiving-telephones at the stations are replaced on theirsupports, the linerelays a are deprived of current and permit theirarmatures to break the connection of battery 6 with the conductors 5 8and 5 9 associated with the respective lines, whereby the indicators ofsupervisory signals 0 and 0 become displayed. Their simultaneousindications may be accepted as a call for disconnection and may befollowed by the removal of plugs g and g from the spring-jacks of theline.

I claim as the invention- 1. The combination with a telephone-lineextending from a subscribers station to a central office, of a signalassociated with the line at the central office, said signal having twodifferential windings, a continuously-active source of current and meansat the subscribers station, actuated during the use of the telephone,for effecting the connection of said source of current with one of thewindings to operate the signal, a circuit including a second winding ofthe said signal differential with respect to the first-mentionedwinding, a source of current in the latter circuit, and switch-contactsclosed in the act of making connection with the line to complete thelastmentioned circuit, whereby the magnet of the signal is renderedinert when connection is made with the line, as described.

2. The combination with a telephone-line extending from a subscribersstation to a central office, of an indicator associated with the line atthe central office, a continuously-active source of current and acircuit including the same with a winding of said indicator, means atthe subscribers station for effecting the completion of said circuitduring the use of the telephone, whereby current is supplied to saidwinding as long as the telephone remains in use, a spring-jack for theline, and plugs and a plug-circuit for making connection therewith, alocal circuit with a source of current therein including a secondwinding of the signal difierential in its effect thereon with respect tothe current controlled from the substation, said local circuit beingcontrolled in registering contact-pieces of the spring-jack and plugduring connection, substantially as and for the purpose specified.

3. The combination with a telephone-line, a source of current and arelay therein, and means at the substation of the line for determiningthe floW of current in the line during the use of the telephone, of alocal circuit controlled by the relay, a source of current therein, anelectromagnetic signal associated with the line having a windingincluded in the said local circuit, a second local circuit including awinding differential with respect to said first-mentioned winding, aspring-jack and a plug for making connection with the line, andregistering switch-contacts in the spring-jack and plug adapted tocomplete the said second-mentioned local circuit, substantially asdescribed.

4:. The combination with a telephone-line having means at its stationfor determining the flow of current in the line automatically in the useof the telephone, of a relay responsive to such current connected withthe line, a spring-jack for the line and a plug and plugci rcuit formaking connection therewith, a local circuit controlled by the relayincluding a source of current, and an electromagnetic signal having awinding in the said 10- cal circuit, a second local circuit alsocontrolled by the relay including a second winding of the said signaldifferential with respect to the first, registering contact-pieces ofthe plug and spring-jack adapted to complete said second-mentioned localcircuit, and a supervisory signal included in the second-mew tionedlocal circuit associated with the plug, substantially as described.

5. The combination with a telephone-line having at its substation meansfor determining the flow of current in the line, a spring jack for theline and a plug and plug-circuit for making connection therewith, and asig nal controlled by such current in the line through the agency of awinding thereon, of alocal circuit completed in registeringswitchcontacts of the spring-jack and plug, a sec ond winding on thesignal-controlling device differential with respect to the first, bothsaid windings being included serially in the said local circuit, and asupervisory signal associated with the plug and interposed in the 1 saidlocal circuit, said supervisory signal be ing also controlled by curentin the telephoneline; whereby connection may be made with the line andthe supervisory'signal may be controlled without causing the display ofthe line-signal, as described.

6. The combination with a telephone-line having means for determiningthe flow of our rent in the line in the use of the telephone, aspring-jack for the line and a plug and plugcircuit for makingconnection therewith, an electromagnetic line-signal associated with theline, said line-signal having two windings, and a supervisory signalassociated with the plug, a relay responsive to current in the line, alocal circuit controlled by the relay divided into two parallelbranches, a winding of said line-signal in each of said branches, saidwindings being difierential with respect to each other, said supervisorysignal being included in one of said branches, and switchcontacts of thespring-jack and plug completing said last-mentioned branch; whereby theline-signal is rendered inert and the supervisory signal is broughtunder the control of the relay when connection is made with the line, asdescribed.

7. The combination with a telephone-line having means at its station fordetermining the flow of current in the line in the use of the telephone,a spring-jack of the line and a plug and plug-circuit for makingconnection therewith, a line-signal associated with the spring-jack,said line-signalhaving two windings, a supervisory signal associatedwith the plug, a relay for the line responsive to current therein, alocal circuit including a battery controlled by the said relay, saidlocal circuit being divided into two parallel branches, a winding of theline-signal being included in each of the branches, said windings beingdifferential with respect to' each other, switch-contacts of thespring-jack and plug completing one of said branches, the supervisorysignal being included in said lastmentioned branch, a source oftest-current insufficient to operate the said signals included in thesame branch, and means for testing the spring-jacks to determine theelectrical condition of the contact-pieces in the local circuit,substantially as described.

8. The combination with a telephone-line extending from a subscribersstation to a central office, of an indicator associated with the line atthe central office, a continuouslyactive source of current, a circuitconnecting the same with a winding of said indicator, and means at thesubscribers station for effecting the completion of such circuit duringthe use of the telephone, whereby said winding is continuously suppliedwith current while the telephone remains in use, a branch circuitconnected in parallel with said firstmentioned circuit and including asecond winding of said indicator difierential with respect to saidfirstn1entioned winding, a spring-jack for the telephone-line and a plugfor making connection therewith, said branch circuit being closed inregistering contacts of the plug and spring-jack, and a supervisorysignal connected with said branch circuit, substantially as set forth.

In witness whereofI hereunto subscribe my name this 2d day of March, A.D. 1897.

CHARLES E. SORIBNER. Witnesses:

ELLA EDLER, JAMES L. MCQUARRIE.

